Typical photographic elements use silver halide emulsions (although other light sensitive materials have been known), silver halide having a native sensitivity to ultraviolet radiation. Ultraviolet radiation ("UV") as used in this application means light having a wavelength of 300-400 nm. Such UV sensitivity is usually undesirable in that it produces an image on the photographic element which is not visible to the human eye. Furthermore, the image dyes in the color photographs are known to fade due to action of UV light. Also other organic molecules such as unused color forming couplers in the emulsion layers and optical brightners in the paper support degrade due to action of UV light and generate undesirable color stains on the finished photographs. Therefore, photographic elements typically contain a UV absorbing compound (sometimes referred to simply as a "UV absorber"). Another function of UV absorbers is to prevent the formation of undesirable patterns caused by electrostatic discharge in silver halide photographic materials. In general, UV absorbers impart light stability to organic molecules in various products which are susceptible to degrade as a result of the action of UV.
Generally, an effective UV absorber should have its peak absorption above a wavelength of 320 nm. The absorption peak may be at a longer wavelength, as long as absorption drops off sufficiently as it approaches the visual range (approximately 400 to 700 nm) so that no visible color is shown by the compound. In addition, to be effective, a UV absorber should have a high extinction coefficient in the desired wavelength range. However, for the most desirable UV protection, the high extinction coefficient should be at those wavelengths sufficiently below the visual range so that the compound should not be visually yellow.
Both conventional and polymeric UV absorbers have been used in photographic elements. Examples of conventional (that is, non-polymeric) UV absorbing compounds are shown by formula (III A) and (III B) below, currently used in color paper as a mixture have the following structures. ##STR2## It has however, been observed that these compounds and other non-polymeric UV absorbers have a propensity to crystallize out in the coatings. This results in migration of the compound to the surface causing an undesirable blooming effect. Recently, it has been suggested that such compounds are associated with high health risk factors.
It is known that polymer latexes obtained by polymerization of UV absorbing monomers, can be utilized as UV absorbing agents which do not have many of the disadvantages associated with non-polymeric UV absorbers. Photographic performance advantages of UV absorbing polymer latexes have been described, for example in U.S. Pat. No. 5,384,235. That patent discloses a polymerizable 2'-hydroxyphenyl benzotriazole having a 5'-position substituent on the 2'-hydroxyphenyl ring chromophore.
U.S. Pat. No. 3,493,539 discloses synthetic solid polymers (that is, plastic materials) containing UV absorbers of the 2'-hydroxyphenyl benzotriazole type. The described UV absorbers for such use can include those having a 4'-substituent with a secondary alcohol substituent (such an --OH substituent sometimes being referenced herein as an "unblocked" or "unprotected" alcohol group). Similar compounds are described for use in sunscreens, suntanning lotions, optical lenses and similar applications, in U.S. Pat. No. 5,099,027 as well as U.S. Pat. Nos. 5,133,745, 3,529,055, 3,445,566, Journal of Macromolecular Science--Pure Applied Chemistry, Vol. A30 (9& 10), page 741-755 (1993)), and Japanese published patent application (Kokai) JP 63205334. Research Disclosure May, 1991, Item 32592 discloses a polymerizable side chain attached to the 5'-position instead of to 4'-position in the hydroxyphenyl ring. The side chain can contain an unprotected secondary alcohol group. U.S. Pat. No. 5,372,922 discloses similar compounds for use in photographic elements. However, the secondary alcohol group is again unblocked.
It is desirable to provide a UV absorbing polymer and photographic elements containing such a polymer, which polymer contains units formed from a 2'-hydroxyphenyl benzotriazole monomer, and which has good stability in a photographic element environment as well as a high extinction co-efficient and a UV absorption which drops rapidly at or near 400 nm and exhibit little or no yellow coloration.